U.S. Pat. No. 5,024,802 shows a method for controlling steam boiler level in a steam generator of a nuclear plant. In a nuclear plant, temperature probes are located in the high temperature fluid flow line or "hotleg", shown in that patent under reference numeral 31. The hotleg temperature is measured in conjunction with the temperature in the cold leg, the return line from the steam generator 34. To measure the temperature, probes such as thermally responsive resistors are placed at various points on a circular plane normal to the fluid flow. A temperature is determined from each sensor. The temperatures for all the sensors are averaged, producing an average temperature (T.sub.H AVG).
The temperature probes (sensors) rarely have the same temperature response characteristics. They produce thermal noise, the level is a function of probe temperature. With thermally responsive probes, the coldest resistance temperature probe may, be the noisiest. The average temperature (T.sub.H AVG) may be incorrect as a result. Repairs are made on the reactor system based upon the average temperature measurements. Therefore, the ability to determine the temperature of the hotleg of the reactor more accurately can translate into less frequent service intervals.